We need to find the expected gain or loss for the store.
This corresponds to the expected value of the variable x with the following possible values and probabilities:
x 1600 800 0
p(x) 20% 75% 5%
We know that the expected value is the sum of the products xp(x), for all possible values of x.
Thus, we obtain:
Answer
The expected gain for the store is $920.